The present invention relates to a technique of judging a state (anomaly or normalcy) of an etching process on the basis of optical emission spectrum distribution obtained by monitoring optical emission of plasma in etching equipment.
To obtain a micro shape of a semiconductor device or the like to be formed on a wafer, an etching process is performed where a substance is ionized by using plasma, and material on the wafer is removed by action (i.e. chemical reaction on the wafer surface) of the ionized substance. Various substances may be used as the substance to be ionized, and the material on the wafer may be different according to the function of the product. Further, to form the shape on the wafer, resist of an organic substance is applied to the wafer, and the shape is formed by photo-lithography, and then the etching process is performed. Further, a substance for adjusting the reaction rate is introduced in order to obtain the predetermined shape. Within a chamber vessel in which the etching process is performed, a variety of substances react with one another.
Ionization by plasma is accompanied by an optical emission phenomenon. Accordingly, etching equipment using plasma in its process is provided with an Optical Emission Spectrometry (OES) to monitor a state of plasma generation.
By monitoring the optical emission phenomenon due to plasma, it is possible to ascertain the performance of the etching process.
Patent Document 1 shows a method in which a plurality of substances are designated, data of the wavelength and magnitude of light emitted by each substance are prepared in a database, and a substance generating a peak is identified. Particularly, Patent Document 1 shows a method in which a learning function improves the accuracy of identification of a substance each time the analysis is performed.    Patent Document 1: Japanese Un-examined Patent Application Laid-Open No. 8-62141